Monthly Archives: February 2012

DrawBot – Pen Selection

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I just tried several pens.  Here’s what I’ve found:

  • “Fine point” Sharpie, black.  This is the kind you typically use.  It makes a huge, stinky, black line that leaks all over.  Not recommended.
  • “Ultra fine point” Sharpie, black.  This also leaked right through the paper, made a super thick line, and made such a mess I stopped the drawing.  Not recommended.
  • Pilot Precise Roling Ball V7, Fine, red.  I really like this style of pen for writing.  These gel pens feed ink easily, the ball point rarely gets messed up, and it’s just all-around easy to use.  Unfortunately, as you can see from some of the drawings, it didn’t like drawing at a nearly horizontal angle.  Even though I can see through the side that the pen has sufficient ink and that it is reaching the pen tip, it just wasn’t working very well.
  • Piolot G-2 10, black.  While excellent for writing, this pen was miserable for use in a DrawBot.
  • Uni-ball Deluxe Micro, blue.  So far, this pen is AWESOME.  It seems to write amazingly well on a nearly horizontal surface, no bleeding, and it draws a very fine line of blue.  I fully intend to buy several different colors of this pen.  I believe it comes in all kinds of colors – black, blue, green, and red.  If the drawing I’m having the robot work on now turns out, you’ll get to see just how awesome this pen really is.

As an FYI, Sandy recommends:

Very smooth paper (like Bristol board) with hard-tipped fineliner pens.  In the UK he uses ZIG Millennium pens.  He suggests that Pigma MICRON pens may be a good choice for those in the states.  I’ve used Pigma Micron pens for years and really like them for pen-and-ink drawing.  They’re great on regular photocopy paper as well as serious art paper.  I would have tried a Pigma pen, but I couldn’t find any around the house.  I know I’ve got a stack of them – I just can’t find ’em.  If and when I do, I’ll update this post.

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DrawBot – Calibration

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Polargraph Calibration by Sandy Noble

Polargraph Calibration by Sandy Noble

Calibrating my DrawBot was apparently important to its operation.  Who knew?!  If you’re following along at home, you’ll definitely want to check out Sandy Noble’s instructible on Polargraph calibration.  I’ll put my settings here, but they probably won’t be that helpful to you unless you’re using the same exact equipment and hardware as I am.

  • Setup->MM per Rev = 50
    • Based on the actual spool center diameter, this should be 47.  But, with some line wound onto the spool, it should be more like 54.  So, of course, I chose something that was neither.
  • Setup->Steps Per Rev = 400
  • Setup->Machine Width = 844
    • Although the “Machine Width” is defined by Sandy as “The distance between the two closest points on the sprockets,” I used a different figure.1  Since my machine uses spools, rather than sprockets, and the spools are unwound on the far side of the spool, I measured from the far edge of the spool’s core the the other far edge of the other spool’s core.  I figure this is probably the best measurement of the width of the line available to the machine.
  • Setup->Machine Height = 848
    • This is a relatively arbitrary specification given that my spools have about four times as much filament than I could use in my current configuration.  I intended this to be 844, but must have typed it in wrong.  :)
  • Setup->Page Width = 216
    • Rounded up from 215.9, which is 8.5 inches converted to millimeters.
  • Setup->Page Height = 279
    • Rounded from 279.4, which is 11 inches converted to millimeters.
  • Setup->Pen Tip Size = 0.12
    • With my 2’x4’x0.5″ board covered in butcher paper, I’ve marked out on the paper the locations of the various important lines for my machine.
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  1. Heaven forbid I do something normal, right? [↩]

DrawBot – Why are you crying?

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Starry Night by Van Gogh, drawn by a freakin’ robot with ADD

Starry Night by Van Gogh, drawn by a freakin’ robot with ADD

After about half an hour I noticed my drawing robot was not making the low scritchy scratchy humming drawing noise.  I’ve started the drawing again…  It looked like it should have been working, the controller software indicated it was still connected, the command queue was still loaded, the Arduino + Motor Shield were still lit up, but it just wasn’t moving.

In retrospect, I should just have hit the reset button on the Arduino.  I think that would have made it pick up with the last command.  But, then I wouldn’t have the lovely picture above to show you!

Actually, I’m really really happy with the drawing quality.  Check out what it looks like when overlaid the subject image:

Starry Night by Van Gogh, drawn by a freakin’ robot with ADD, overlaid the subject image

Starry Night by Van Gogh, drawn by a freakin’ robot with ADD, overlaid the subject image

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You know there’s something wrong when…

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My office is about two blocks from a grocery store and many days I’ll just walk out there and grab a sandwich from the deli.  As I was walking back I thought of something I might want to blog…  but none of my current blogs1 was particularly appropriate for this notion.  For a full minute I actually toyed with the idea of starting a fourth.

Which, of course, is just pure madness.  There’s no damn reason for one man to blog in four places across the internet. 234

Thankfully that moment of madness has passed and I have no recollection of the thought which prompted me to taste insanity just before my turkey wrap.5

  1. I post two places regularly and on a third site very infrequently. [↩]
  2. Unless, of course, schizophrenia counts as “reason.”  And, I’m pretty sure it’s the opposite. [↩]
  3. Or close enough to the opposite of reason when one considers the appropriate number of blogs per capita. [↩]
  4. One man, one vote, and one blog seems about right. [↩]
  5. Except for the lingering knowledge that I had some thought/idea that was so compelling I might actually decide to spin up a fourth blog. [↩]

DrawBot – Printing, Part II

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After actually calibrating my machine, the results are MUCH better.  I still need to adjust the settings a little, but otherwise I’m very very happy with this result.  As you can see, the drawing is flipped.  Once flipped back, I think it is reasonably apparent this is Van Gogh’s Starry Night.  Here are a few things I’m going to try:

  • The pen I was using seemed to stop working in certain regions of the drawing.  I bought a few new pens on my lunch break today.  Both are art marker pens – one blue and one red.  Unfortunately, both are too wide to fit in my current gondola.  For now I’ll use a thin sharpie.
  • There is a slight curvature on the top and bottom of the drawing.  This is probably due to a miscalculation in the mm per rotation.  The downside to using a spool, rather than a sprocket/ball chain or gear/toothed belt, is that as the spool contains more cord, the diameter of the spool actually grows larger.  This means that when there’s a lot of line on the spool each rotation releases more line and when there’s very little line left on the spool, each rotate releases less line.  However, given the diminished space requirements, I don’t think this is going to be such a big deal.
  • I mostly measured the machine width.  Basically what that means is that I did measure it, but then got distracted, then used what I recalled the width to be inches to calculate the width in mm.  Clearly, there is room for increased precision.
  • For weights I’m using a bunch of spent batteries in a ziplock baggie tied with a wire to the gondola.  Too many batteries were causing the line to be too jagged.
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DrawBot – Printing!

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I’ve actually printed something using my DrawBot!!!  Would you like to see it?!

DrawBot test print #4

DrawBot test print #4

As you can see, this is a print of Van Gogh’s Starry Night.  It has a few problems.  First, the pen was non-ideal.  This will take some experimentation.  Second, the image, as anyone can tell you, is mirrored.  Third, the image was supposed to be much larger – almost as wide as the entire A4 page I’ve scanned in above.  I fiddled with some settings last night, but didn’t accomplish much.  I’ll try again tonight.

However!  I’m really very encouraged!  It actually drew something that roughly corresponds to the thing I’ve asked it to draw!  I’m looking forward to playing with the settings.  The robot is fairly quiet – it’s propped against a wall about seven feet from where I’m sitting and the sound of operation is barely noticeable above the television.

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DrawBot – The Breakdown, Part II

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Since my prior cost breakdown post, I’ve invested a little more in this project.  Thankfully, this hasn’t been a project where I’ve been throwing money at the end goal.  Overall, it’s been incredibly cheap with the cost of failure at the most delicate points being quite low.this help in choosing the steppers and power adapter.  Here’s what I bought and from where:

Right now the robot is probably close to its final form and I don’t anticipate any further expenditures.  Someone who has a box of electronic stuff could almost certainly build this robot for next to nothing.  Many other people have spare Arduinos, steppers, stepper controllers, and power supplies.  If I just purchased the bare minimum for this project and used scrap stuff from around the house, I probably could have built this robot even cheaper.

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  1. I couldn’t think of anything else I couldn’t live without!! [↩]

DrawBot – The Assembly, Part VIII

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Well, my newly designed motor mounts, while cool, just aren’t working.  If I were committed to using that long pine box, I could probably make a go of them.  I’ve tried several variations on this robot, and nothing has really worked so far.  Here’s what I’ve tried:

  1. In a box, mounted to the wall
    1. This just didn’t work.  The spot I found on the wall was in our robot room, behind my monstrous card catalog.  It was difficult to get to, the laptop I had it hooked up to wasn’t really talking to the robot, and I didn’t even get it fully hooked up in that location before I decided it just wasn’t going to work.
  2. In a box, under an easel
    1. In a fit of inspiration I realized that I had a painting easel, a rather nice one at that.  I took an old new canvas1 , put it on the easel, put the easel’s feet inside the long pine box, ran the monofilament line from the motor, through holes in the pine box, up behind the canvas, through an eyescrew on top of the canvas, and down over the front.  This was terrible.  It creaked, shuddered, and the pen sputtered around the front.
  3. In a box, on an easel
    1. Not ready to give up on Project Easel, I tried to put the pine box on top of the canvas and hold them together in the easel.  This really didn’t work.  Because of the location of the motors in the pine box, the canvas was either going to block the holes for the monofilament line or I’d have to run the line through the top of the box, which would have resulted in the same creaky, shuddering, sputtering problem of using the line through a hole in the box as if it were a pulley.  Either way, the entire assembly just wasn’t stable on the easel which did not want to hold it together.
  4. Bolted to a chunk of wood
    1. I actually have some spare plywood, but it’s been in the garage for a while and has a weathered look to it.  It also has a large 1.5 foot radius quarter circle cut out of it.  I figure if I’m going to keep this inside, I might as well spring for a new piece of wood.  A bit over $14 at the hardware store and I was in business.  Now that I’ve given up on my nifty motor mounts, I designed and printed a dead simple motor mount.  I could have accomplished much the same result by just drilling some holes in a piece of scrap wood. 2  I’ve also abandoned a gondola of my own design. 3
    2. The final result is essentially as follows – a 2’x4’x0.5″ piece of plywood, wrapped in butcher paper, two steppers bolted to mounts and screwed to the left and right sides at the end of the plywood.  The steppers are wired to the stepper motor in the center, and the Arduino and stepper motor controller are in an ill-fitting plastic holder which is duct taped to the front top of the plywood.  The plywood is then propped up against our built-in on which my most useless laptop is sitting, ready to run the robot.
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  1. Old because I’ve had it for about 10 years; new because it’s still in the shrink wrap.  Now, to my credit, I have actually painted on my other canvases – this is just the last one and I completely forgot about it. [↩]
  2. These will probably have been the very very last thing I’ll have ever printed with my black ABS. [↩]
  3. While cool, it just did not work well at all – I made the pen holder so large it would only hold the largest sharpie made by man, it didn’t do a good job of holding the pen against the paper, and it held the weights rather awkwardly. [↩]

Roboapocalypse averted

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Yesterday I got to hang out with Chris of DIYDrones.  We discussed this video and he assured me that SkyNet is still a little ways off.

What I didn’t realize about those videos is that they are, in Chris’ words, one step up from a simulation.  The rooms in which those copters are flying have no turbulence, are surrounded by sensors, all obstacles are clearly marked so that they can be picked out by the myriad of cameras surrounding the room, and all of the sensing and computing is being done by a computer – rather than the drones themselves.

Even if you had an army of robo-drones that could only fly indoors, how cool would that be?  Some of those videos show the little ‘bots lifting and assembling structures.  I would love to have a swarm of these things that did nothing but structures out of legos.

Now, I suppose, I only have to concern myself with the zombie apocalypse.